| Abstract |
The development of a two-dimensional hydro-thermal fracture model applicable to Enhanced Geothermal Systems (EGS) using boundary element method (BEM) is presented in this paper. The hydro-thermal fracturing process in the EGS reservoirs is a combination of many complicated physical phenomena, including fracture opening and closure in elastic geologic materials, nonlinear behavior of injected slurry, fracture propagation in rock mass, proppant transportation and it’s action to prevent fracture closure, flow of fluid and heat though the fracture and the surrounding rock. Two-dimensional Displacement Discontinuity method (DDM) for an elastic medium using indirect formulation of BEM is used to model the relationship of fracture aperture and stress distribution around the fracture. Injection of fracturing fluid during stimulation with different temperature from the target rock temperature will induce heat conduction between fracturing fluid and reservoir rocks. Two-dimensional transient heat flow model was developed using the explicit finite difference method to estimate thermal-induced effects on fracture geometry. The fluid temperature distribution inside the fracture was approximated by solution of one-dimensional advection-diffusion process. The thermal induced fracture geometry changes were coupled with those from hydraulic fracturing geometry changes. A parametric study was done to quantify the effects of differential cooling temperature of reservoir rocks due to fluid injection on fracture geometry. |